A secondary battery device which includes a battery such as a lithium ion battery and a controller such as a battery management unit (BMU) managing the battery has been known. As an example of the battery management unit, there is a device which performs controller area network (CAN) communication with an engine controller as a host device, and the like, to transmit a voltage, a temperature, and the like of the battery to the host device.
In addition, the controller alone may sometimes operate to monitor and evaluate the battery without communicating with the host device. In this case, it is conceivable to attach a connector (dummy connector) starting the controller to a control connector of the secondary battery device to start the BMU.
While the dummy connector is attached (connected) to the control connector, the power of the battery is consumed by the operation of the controller. For this reason, if a user mistakes the dummy connector for a protective cap of the control connector and the dummy connector is left attached to the secondary battery device, the power of the battery is consumed against the user's intention.